/******************************************************************************

*

 * Project:  GDAL

 * Purpose:  "gdal vector combine" subcommand

 * Author:   Daniel Baston

 *

 ******************************************************************************

 * Copyright (c) 2025-2026, ISciences LLC

 *

 * SPDX-License-Identifier: MIT

 ****************************************************************************/

#include "gdalalg_vector_combine.h"

#include "cpl_enumerate.h"

#include "cpl_error.h"

#include "gdal_priv.h"

#include "gdalalg_vector_geom.h"

#include "ogr_geometry.h"

#include <algorithm>

#include <cinttypes>

#include <optional>

#ifndef _

#define _(x) (x)

#endif

//! @cond Doxygen_Suppress

GDALVectorCombineAlgorithm::GDALVectorCombineAlgorithm(bool standaloneStep)

    : GDALVectorPipelineStepAlgorithm(NAME, DESCRIPTION, HELP_URL,

                                      standaloneStep)

{

    auto &groupByArg =

        AddArg("group-by", 0,

               _("Names of field(s) by which inputs should be grouped"),

               &m_groupBy)

            .SetDuplicateValuesAllowed(false);

    SetAutoCompleteFunctionForFieldName(

        groupByArg, GetArg(GDAL_ARG_NAME_INPUT_LAYER),

        /* attributeFields = */ true,

        /* geometryFields = */ false, m_inputDataset);

    AddArg("keep-nested", 0,

           _("Avoid combining the components of multipart geometries"),

           &m_keepNested);

    AddArg("add-extra-fields", 0,

           _("Whether to add extra fields, depending on if they have identical "

             "values within each group"),

           &m_addExtraFields)

        .SetChoices(NO, SOMETIMES_IDENTICAL, ALWAYS_IDENTICAL)

        .SetDefault(m_addExtraFields)

        .AddValidationAction(

            [this]()

            {

                // We check the SQLITE driver availability, because we need to

                // issue a SQL request using the SQLITE dialect, but that works

                // on any source dataset.

                if (m_addExtraFields != NO &&

                    GetGDALDriverManager()->GetDriverByName("SQLITE") ==

                        nullptr)

                {

                    ReportError(CE_Failure, CPLE_NotSupported,

                                "The SQLITE driver must be available for "

                                "add-extra-fields=%s",

                                m_addExtraFields.c_str());

                    return false;

                }

                return true;

            });

}

namespace

{

class GDALVectorCombineOutputLayer final

    : public GDALVectorNonStreamingAlgorithmLayer

{

    /** Identify which fields have, at least for one group, the same

     * value within the rows of the group, and add them to the destination

     * feature definition, after the group-by fields.

     */

    void IdentifySrcFieldsThatCanBeCopied(GDALDataset &srcDS,

                                          const std::string &addExtraFields)

    {

        const OGRFeatureDefn *srcDefn = m_srcLayer.GetLayerDefn();

        if (srcDefn->GetFieldCount() > static_cast<int>(m_groupBy.size()))

        {

            std::vector<std::pair<std::string, int>> extraFieldCandidates;

            const auto itSrcFields = srcDefn->GetFields();

            for (const auto [iSrcField, srcFieldDefn] :

                 cpl::enumerate(itSrcFields))

            {

                const char *fieldName = srcFieldDefn->GetNameRef();

                if (std::find(m_groupBy.begin(), m_groupBy.end(), fieldName) ==

                    m_groupBy.end())

                {

                    extraFieldCandidates.emplace_back(

                        fieldName, static_cast<int>(iSrcField));

                }

            }

            std::string sql("SELECT ");

            bool addComma = false;

            for (const auto &[fieldName, _] : extraFieldCandidates)

            {

                if (addComma)

                    sql += ", ";

                addComma = true;

                if (addExtraFields ==

                    GDALVectorCombineAlgorithm::ALWAYS_IDENTICAL)

                    sql += "MIN(";

                else

                    sql += "MAX(";

                sql += CPLQuotedSQLIdentifier(fieldName.c_str());

                sql += ')';

            }

            sql += " FROM (SELECT ";

            addComma = false;

            for (const auto &[fieldName, _] : extraFieldCandidates)

            {

                if (addComma)

                    sql += ", ";

                addComma = true;

                sql += "(COUNT(DISTINCT COALESCE(";

                sql += CPLQuotedSQLIdentifier(fieldName.c_str());

                sql += ", '__NULL__')) == 1) AS ";

                sql += CPLQuotedSQLIdentifier(fieldName.c_str());

            }

            sql += " FROM ";

            sql += CPLQuotedSQLIdentifier(GetLayerDefn()->GetName());

            if (!m_groupBy.empty())

            {

                sql += " GROUP BY ";

                addComma = false;

                for (const auto &fieldName : m_groupBy)

                {

                    if (addComma)

                        sql += ", ";

                    addComma = true;

                    sql += CPLQuotedSQLIdentifier(fieldName.c_str());

                }

            }

            sql += ") dummy_table_name";

            auto poSQLyr = srcDS.ExecuteSQL(sql.c_str(), nullptr, "SQLite");

            if (poSQLyr)

            {

                auto poResultFeature =

                    std::unique_ptr<OGRFeature>(poSQLyr->GetNextFeature());

                if (poResultFeature)

                {

                    CPLAssert(poResultFeature->GetFieldCount() ==

                              static_cast<int>(extraFieldCandidates.size()));

                    for (const auto &[iSqlCol, srcFieldInfo] :

                         cpl::enumerate(extraFieldCandidates))

                    {

                        const int iSrcField = srcFieldInfo.second;

                        if (poResultFeature->GetFieldAsInteger(

                                static_cast<int>(iSqlCol)) == 1)

                        {

                            m_defn->AddFieldDefn(

                                srcDefn->GetFieldDefn(iSrcField));

                            m_srcExtraFieldIndices.push_back(iSrcField);

                        }

                        else

                        {

                            CPLDebugOnly(

                                "gdalalg_vector_combine",

                                "Field %s has the same values within a group",

                                srcFieldInfo.first.c_str());

                        }

                    }

                }

                srcDS.ReleaseResultSet(poSQLyr);

            }

        }

    }

  public:

    explicit GDALVectorCombineOutputLayer(

        GDALDataset &srcDS, OGRLayer &srcLayer, int geomFieldIndex,

        const std::vector<std::string> &groupBy, bool keepNested,

        const std::string &addExtraFields)

        : GDALVectorNonStreamingAlgorithmLayer(srcLayer, geomFieldIndex),

          m_groupBy(groupBy), m_defn(OGRFeatureDefnRefCountedPtr::makeInstance(

                                  srcLayer.GetLayerDefn()->GetName())),

          m_keepNested(keepNested)

    {

        const OGRFeatureDefn *srcDefn = m_srcLayer.GetLayerDefn();

        // Copy field definitions for attribute fields used in

        // --group-by. All other attributes are discarded.

        for (const auto &fieldName : m_groupBy)

        {

            // RunStep already checked that the field exists

            const auto iField = srcDefn->GetFieldIndex(fieldName.c_str());

            CPLAssert(iField >= 0);

            m_srcGroupByFieldIndices.push_back(iField);

            m_defn->AddFieldDefn(srcDefn->GetFieldDefn(iField));

        }

        if (addExtraFields != GDALVectorCombineAlgorithm::NO)

            IdentifySrcFieldsThatCanBeCopied(srcDS, addExtraFields);

        // Create a new geometry field corresponding to each input geometry

        // field. An appropriate type is worked out below.

        m_defn->SetGeomType(wkbNone);  // Remove default geometry field

        for (const OGRGeomFieldDefn *srcGeomDefn : srcDefn->GetGeomFields())

        {

            const auto eSrcGeomType = srcGeomDefn->GetType();

            const bool bHasZ = CPL_TO_BOOL(OGR_GT_HasZ(eSrcGeomType));

            const bool bHasM = CPL_TO_BOOL(OGR_GT_HasM(eSrcGeomType));

            OGRwkbGeometryType eDstGeomType =

                OGR_GT_SetModifier(wkbGeometryCollection, bHasZ, bHasM);

            // If the layer claims to have single-part geometries, choose a more

            // specific output type like "MultiPoint" rather than "GeometryCollection"

            if (wkbFlatten(eSrcGeomType) != wkbUnknown &&

                !OGR_GT_IsSubClassOf(wkbFlatten(eSrcGeomType),

                                     wkbGeometryCollection))

            {

                eDstGeomType = OGR_GT_GetCollection(eSrcGeomType);

            }

            auto dstGeomDefn = std::make_unique<OGRGeomFieldDefn>(

                srcGeomDefn->GetNameRef(), eDstGeomType);

            dstGeomDefn->SetSpatialRef(srcGeomDefn->GetSpatialRef());

            m_defn->AddGeomFieldDefn(std::move(dstGeomDefn));

        }

    }

    GIntBig GetFeatureCount(int bForce) override

    {

        if (m_poAttrQuery == nullptr && m_poFilterGeom == nullptr)

        {

            return static_cast<GIntBig>(m_features.size());

        }

        return OGRLayer::GetFeatureCount(bForce);

    }

    const OGRFeatureDefn *GetLayerDefn() const override

    {

        return m_defn.get();

    }

    OGRErr IGetExtent(int iGeomField, OGREnvelope *psExtent,

                      bool bForce) override

    {

        return m_srcLayer.GetExtent(iGeomField, psExtent, bForce);

    }

    OGRErr IGetExtent3D(int iGeomField, OGREnvelope3D *psExtent,

                        bool bForce) override

    {

        return m_srcLayer.GetExtent3D(iGeomField, psExtent, bForce);

    }

    std::unique_ptr<OGRFeature> GetNextProcessedFeature() override

    {

        if (!m_itFeature)

        {

            m_itFeature = m_features.begin();

        }

        if (m_itFeature.value() == m_features.end())

        {

            return nullptr;

        }

        std::unique_ptr<OGRFeature> feature(

            m_itFeature.value()->second->Clone());

        feature->SetFID(m_nProcessedFeaturesRead++);

        ++m_itFeature.value();

        return feature;

    }

    bool Process(GDALProgressFunc pfnProgress, void *pProgressData) override

    {

        const int nGeomFields = m_srcLayer.GetLayerDefn()->GetGeomFieldCount();

        const GIntBig nLayerFeatures =

            m_srcLayer.TestCapability(OLCFastFeatureCount)

                ? m_srcLayer.GetFeatureCount(false)

                : -1;

        const double dfInvLayerFeatures =

            1.0 / std::max(1.0, static_cast<double>(nLayerFeatures));

        GIntBig nFeaturesRead = 0;

        struct PairSourceFeatureUniqueValues

        {

            std::unique_ptr<OGRFeature> poSrcFeature{};

            std::vector<std::optional<std::string>> srcUniqueValues{};

        };

        std::map<OGRFeature *, PairSourceFeatureUniqueValues>

            mapDstFeatureToOtherFields;

        std::vector<std::string> fieldValues(m_srcGroupByFieldIndices.size());

        std::vector<std::string> extraFieldValues(

            m_srcExtraFieldIndices.size());

        std::vector<int> srcDstFieldMap(

            m_srcLayer.GetLayerDefn()->GetFieldCount(), -1);

        for (const auto [iDstField, iSrcField] :

             cpl::enumerate(m_srcGroupByFieldIndices))

        {

            srcDstFieldMap[iSrcField] = static_cast<int>(iDstField);

        }

        for (const auto &srcFeature : m_srcLayer)

        {

            for (const auto [iDstField, iSrcField] :

                 cpl::enumerate(m_srcGroupByFieldIndices))

            {

                fieldValues[iDstField] =

                    srcFeature->GetFieldAsString(iSrcField);

            }

            for (const auto [iExtraField, iSrcField] :

                 cpl::enumerate(m_srcExtraFieldIndices))

            {

                extraFieldValues[iExtraField] =

                    srcFeature->GetFieldAsString(iSrcField);

            }

            OGRFeature *dstFeature;

            if (auto it = m_features.find(fieldValues); it == m_features.end())

            {

                it = m_features

                         .insert(std::pair(

                             fieldValues,

                             std::make_unique<OGRFeature>(m_defn.get())))

                         .first;

                dstFeature = it->second.get();

                dstFeature->SetFrom(srcFeature.get(), srcDstFieldMap.data(),

                                    false);

                for (int iGeomField = 0; iGeomField < nGeomFields; iGeomField++)

                {

                    OGRGeomFieldDefn *poGeomDefn =

                        m_defn->GetGeomFieldDefn(iGeomField);

                    const auto eGeomType = poGeomDefn->GetType();

                    std::unique_ptr<OGRGeometry> poGeom(

                        OGRGeometryFactory::createGeometry(eGeomType));

                    poGeom->assignSpatialReference(poGeomDefn->GetSpatialRef());

                    dstFeature->SetGeomField(iGeomField, std::move(poGeom));

                }

                if (!m_srcExtraFieldIndices.empty())

                {

                    PairSourceFeatureUniqueValues pair;

                    pair.poSrcFeature.reset(srcFeature->Clone());

                    for (const std::string &s : extraFieldValues)

                        pair.srcUniqueValues.push_back(s);

                    mapDstFeatureToOtherFields[dstFeature] = std::move(pair);

                }

            }

            else

            {

                dstFeature = it->second.get();

                // Check that the extra field values for that source feature

                // are the same as for other source features of the same group.

                // If not the case, cancel the extra field value for that group.

                if (!m_srcExtraFieldIndices.empty())

                {

                    auto iterOtherFields =

                        mapDstFeatureToOtherFields.find(dstFeature);

                    CPLAssert(iterOtherFields !=

                              mapDstFeatureToOtherFields.end());

                    auto &srcUniqueValues =

                        iterOtherFields->second.srcUniqueValues;

                    CPLAssert(srcUniqueValues.size() ==

                              extraFieldValues.size());

                    for (const auto &[i, sVal] :

                         cpl::enumerate(extraFieldValues))

                    {

                        if (srcUniqueValues[i].has_value() &&

                            *(srcUniqueValues[i]) != sVal)

                        {

                            srcUniqueValues[i].reset();

                        }

                    }

                }

            }

            for (int iGeomField = 0; iGeomField < nGeomFields; iGeomField++)

            {

                OGRGeomFieldDefn *poGeomFieldDefn =

                    m_defn->GetGeomFieldDefn(iGeomField);

                std::unique_ptr<OGRGeometry> poSrcGeom(

                    srcFeature->StealGeometry(iGeomField));

                if (poSrcGeom != nullptr && !poSrcGeom->IsEmpty())

                {

                    const auto eSrcType = poSrcGeom->getGeometryType();

                    const auto bSrcIsCollection = OGR_GT_IsSubClassOf(

                        wkbFlatten(eSrcType), wkbGeometryCollection);

                    const auto bDstIsUntypedCollection =

                        wkbFlatten(poGeomFieldDefn->GetType()) ==

                        wkbGeometryCollection;

                    // Did this geometry unexpectedly have Z?

                    if (OGR_GT_HasZ(eSrcType) !=

                        OGR_GT_HasZ(poGeomFieldDefn->GetType()))

                    {

                        AddZ(iGeomField);

                    }

                    // Did this geometry unexpectedly have M?

                    if (OGR_GT_HasM(eSrcType) !=

                        OGR_GT_HasM(poGeomFieldDefn->GetType()))

                    {

                        AddM(iGeomField);

                    }

                    // Do we need to change the output from a typed collection

                    // like MultiPolygon to a generic GeometryCollection?

                    if (m_keepNested && bSrcIsCollection &&

                        !bDstIsUntypedCollection)

                    {

                        SetTypeGeometryCollection(iGeomField);

                    }

                    OGRGeometryCollection *poDstGeom =

                        cpl::down_cast<OGRGeometryCollection *>(

                            dstFeature->GetGeomFieldRef(iGeomField));

                    if (m_keepNested || !bSrcIsCollection)

                    {

                        if (poDstGeom->addGeometry(std::move(poSrcGeom)) !=

                            OGRERR_NONE)

                        {

                            CPLError(

                                CE_Failure, CPLE_AppDefined,

                                "Failed to add geometry of type %s to output "

                                "feature of type %s",

                                OGRGeometryTypeToName(eSrcType),

                                OGRGeometryTypeToName(

                                    poDstGeom->getGeometryType()));

                            return false;

                        }

                    }

                    else

                    {

                        std::unique_ptr<OGRGeometryCollection>

                            poSrcGeomCollection(

                                poSrcGeom.release()->toGeometryCollection());

                        if (poDstGeom->addGeometryComponents(

                                std::move(poSrcGeomCollection)) != OGRERR_NONE)

                        {

                            CPLError(CE_Failure, CPLE_AppDefined,

                                     "Failed to add components from geometry "

                                     "of type %s to output "

                                     "feature of type %s",

                                     OGRGeometryTypeToName(eSrcType),

                                     OGRGeometryTypeToName(

                                         poDstGeom->getGeometryType()));

                            return false;

                        }

                    }

                }

            }

            if (pfnProgress && nLayerFeatures > 0 &&

                !pfnProgress(static_cast<double>(++nFeaturesRead) *

                                 dfInvLayerFeatures,

                             "", pProgressData))

            {

                CPLError(CE_Failure, CPLE_UserInterrupt, "Interrupted by user");

                return false;

            }

        }

        // Copy extra fields from source features that have a same value

        // among each groups

        for (const auto &[poDstFeature, pairSourceFeatureUniqueValues] :

             mapDstFeatureToOtherFields)

        {

            for (const auto [iExtraField, iSrcField] :

                 cpl::enumerate(m_srcExtraFieldIndices))

            {

                const int iDstField = static_cast<int>(

                    m_srcGroupByFieldIndices.size() + iExtraField);

                if (pairSourceFeatureUniqueValues.srcUniqueValues[iExtraField])

                {

                    const auto poRawField =

                        pairSourceFeatureUniqueValues.poSrcFeature

                            ->GetRawFieldRef(iSrcField);

                    poDstFeature->SetField(iDstField, poRawField);

                }

            }

        }

        if (pfnProgress)

        {

            pfnProgress(1.0, "", pProgressData);

        }

        return true;

    }

    int TestCapability(const char *pszCap) const override

    {

        if (EQUAL(pszCap, OLCFastFeatureCount))

        {

            return true;

        }

        if (EQUAL(pszCap, OLCStringsAsUTF8) ||

            EQUAL(pszCap, OLCFastGetExtent) ||

            EQUAL(pszCap, OLCFastGetExtent3D) ||

            EQUAL(pszCap, OLCCurveGeometries) ||

            EQUAL(pszCap, OLCMeasuredGeometries) ||

            EQUAL(pszCap, OLCZGeometries))

        {

            return m_srcLayer.TestCapability(pszCap);

        }

        return false;

    }

    void ResetReading() override

    {

        m_itFeature.reset();

        m_nProcessedFeaturesRead = 0;

    }

    CPL_DISALLOW_COPY_ASSIGN(GDALVectorCombineOutputLayer)

  private:

    void AddM(int iGeomField)

    {

        OGRGeomFieldDefn *poGeomFieldDefn =

            m_defn->GetGeomFieldDefn(iGeomField);

        whileUnsealing(poGeomFieldDefn)

            ->SetType(OGR_GT_SetM(poGeomFieldDefn->GetType()));

        for (auto &[_, poFeature] : m_features)

        {

            poFeature->GetGeomFieldRef(iGeomField)->setMeasured(true);

        }

    }

    void AddZ(int iGeomField)

    {

        OGRGeomFieldDefn *poGeomFieldDefn =

            m_defn->GetGeomFieldDefn(iGeomField);

        whileUnsealing(poGeomFieldDefn)

            ->SetType(OGR_GT_SetZ(poGeomFieldDefn->GetType()));

        for (auto &[_, poFeature] : m_features)

        {

            poFeature->GetGeomFieldRef(iGeomField)->set3D(true);

        }

    }

    void SetTypeGeometryCollection(int iGeomField)

    {

        OGRGeomFieldDefn *poGeomFieldDefn =

            m_defn->GetGeomFieldDefn(iGeomField);

        const bool hasZ = CPL_TO_BOOL(OGR_GT_HasZ(poGeomFieldDefn->GetType()));

        const bool hasM = CPL_TO_BOOL(OGR_GT_HasM(poGeomFieldDefn->GetType()));

        whileUnsealing(poGeomFieldDefn)

            ->SetType(OGR_GT_SetModifier(wkbGeometryCollection, hasZ, hasM));

        for (auto &[_, poFeature] : m_features)

        {

            std::unique_ptr<OGRGeometry> poTmpGeom(

                poFeature->StealGeometry(iGeomField));

            poTmpGeom = OGRGeometryFactory::forceTo(std::move(poTmpGeom),

                                                    poGeomFieldDefn->GetType());

            CPLAssert(poTmpGeom);

            poFeature->SetGeomField(iGeomField, std::move(poTmpGeom));

        }

    }

    const std::vector<std::string> m_groupBy{};

    std::vector<int> m_srcGroupByFieldIndices{};

    std::vector<int> m_srcExtraFieldIndices{};

    std::map<std::vector<std::string>, std::unique_ptr<OGRFeature>>

        m_features{};

    std::optional<decltype(m_features)::const_iterator> m_itFeature{};

    const OGRFeatureDefnRefCountedPtr m_defn;

    GIntBig m_nProcessedFeaturesRead = 0;

    const bool m_keepNested;

};

}  // namespace

bool GDALVectorCombineAlgorithm::RunStep(GDALPipelineStepRunContext &ctxt)

{

    auto poSrcDS = m_inputDataset[0].GetDatasetRef();

    auto poDstDS =

        std::make_unique<GDALVectorNonStreamingAlgorithmDataset>(*poSrcDS);

    GDALVectorAlgorithmLayerProgressHelper progressHelper(ctxt);

    for (auto &&poSrcLayer : poSrcDS->GetLayers())

    {

        if (m_inputLayerNames.empty() ||

            std::find(m_inputLayerNames.begin(), m_inputLayerNames.end(),

                      poSrcLayer->GetDescription()) != m_inputLayerNames.end())

        {

            const auto poSrcLayerDefn = poSrcLayer->GetLayerDefn();

            if (poSrcLayerDefn->GetGeomFieldCount() == 0)

            {

                if (m_inputLayerNames.empty())

                    continue;

                ReportError(CE_Failure, CPLE_AppDefined,

                            "Specified layer '%s' has no geometry field",

                            poSrcLayer->GetDescription());

                return false;

            }

            // Check that all attributes exist

            for (const auto &fieldName : m_groupBy)

            {

                const int iSrcFieldIndex =

                    poSrcLayerDefn->GetFieldIndex(fieldName.c_str());

                if (iSrcFieldIndex == -1)

                {

                    ReportError(CE_Failure, CPLE_AppDefined,

                                "Specified attribute field '%s' does not exist "

                                "in layer '%s'",

                                fieldName.c_str(),

                                poSrcLayer->GetDescription());

                    return false;

                }

            }

            progressHelper.AddProcessedLayer(*poSrcLayer);

        }

    }

    for ([[maybe_unused]] auto [poSrcLayer, bProcessed, layerProgressFunc,

                                layerProgressData] : progressHelper)

    {

        auto poLayer = std::make_unique<GDALVectorCombineOutputLayer>(

            *poSrcDS, *poSrcLayer, -1, m_groupBy, m_keepNested,

            m_addExtraFields);

        if (!poDstDS->AddProcessedLayer(std::move(poLayer), layerProgressFunc,

                                        layerProgressData.get()))

        {

            return false;

        }

    }

    m_outputDataset.Set(std::move(poDstDS));

    return true;

}

GDALVectorCombineAlgorithmStandalone::~GDALVectorCombineAlgorithmStandalone() =

    default;

//! @endcond